Background Several studies have shown mechanical alignment influences the outcome of TKA. Robotic systems have been developed to improve the precision and accuracy of achieving component position and mechanical alignment. Questions/purposes We determined whether roboticassisted implantation for TKA (1) improved clinical outcome; (2) improved mechanical axis alignment and implant inclination in the coronal and sagittal planes; (3) improved the balance (flexion and extension gaps); and (4) reduced complications, postoperative drainage, and operative time when compared to conventionally implanted TKA over an intermediate-term (minimum 3-year) followup period. MethodsWe prospectively randomized 100 patients who underwent unilateral TKA into one of two groups: 50 using a robotic-assisted procedure and 50 using conventional manual techniques. Outcome variables considered were postoperative ROM, WOMAC scores, Hospital for Special Surgery (HSS) knee scores, mechanical axis alignment, flexion/extension gap balance, complications, postoperative drainage, and operative time. Minimum followup was 41 months (mean, 65 months; range, 41-81 months). Results There were no differences in postoperative ROM, WOMAC scores, and HSS knee scores. The roboticassisted group resulted in no mechanical axis outliers ([ ± 3°from neutral) compared to 24% in the conventional group. There were fewer robotic-assisted knees

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The menisci play an important role in load distribution, load bearing, joint stability, lubrication, and proprioception. Partial meniscectomy has been shown to result in changes in the kinematics and kinetics at the knee during gait that can lead to progressive meniscal degeneration. This study examined changes in the strains within the menisci associated with kinematic and kinetic changes during the gait cycle. The gait changes considered were a 5 deg shift toward external rotation of the tibia with respect to the femur and an increased medial-lateral load ratio representing an increased adduction moment. A finite element model of the knee was developed and tested using a cadaveric specimen. The cadaver was placed in positions representing heel-strike and midstance of the normal gait, and magnetic resonance images were taken. Comparisons of the model predictions to boundaries digitized from images acquired in the loaded states were within the errors produced by a 1 pixel shift of either meniscus. The finite element model predicted that an increased adduction moment caused increased strains of both the anterior and posterior horns of the medial meniscus. The lateral meniscus exhibited much lower strains and had minimal changes under the various loading conditions. The external tibial rotational change resulted in a 20% decrease in the strains in the posterior medial horn and increased strains in the anterior medial horn. The results of this study suggest that the shift toward external tibial rotation seen clinically after partial medial meniscectomy is not likely to cause subsequent degenerative medial meniscal damage, but the consequence of this kinematic shift on the pathogenesis of osteoarthritis following meniscectomy requires further consideration.

Knee arthroplasty is used to treat patients with degenerative joint disease of the knee to reduce pain and restore the function of the joint. Although patient outcomes are generally quite good, there are still a number of patients that are dissatisfied with their procedures. Aside from implant design which has largely become standard, surgical technique is one of the main factors that determine clinical results. Therefore, a lot of effort has gone into improving surgical technique including the use of computer-aided surgery. The latest generation of orthopedic surgical tools involves the use of robotics to enhance the surgeons' abilities to install implants more precisely and consistently. This review presents an evolution of robot-assisted surgical systems for knee replacement with an emphasis on the clinical results available in the literature. Ever since various robotic-assistance systems were developed and used clinically worldwide, studies have demonstrated that these systems are as safe as and more accurate than conventional methods of manual implantation. Robotic surgical assistance will likely result in improved surgical technique and improved clinical results.